1. Field of the Invention
The present invention relates to systems and methods for managing inertial torque reaction of rotating machines.
2. Background Art
A conventional powertrain has a “stationary” structure that is attached to the vehicle chassis with resilient mounts. In conventional powertrains, various engine and transmission components including the crankshaft, flywheel, and torque converter of an automatic transmission, for example, rotate in the same direction such that their rotating inertia has a compounding effect. When a compression or combustion event of the engine causes an acceleration of the rotating inertia, generally, there is an equal but opposite inertial torque reaction imposed upon the stationary structure. As such, the stationary structure is not truly stationary, but instead, vibrates in opposition to the accelerations of the rotating inertia. This vibration of the stationary structure passes vibration through the resilient mounts into the vehicle chassis, and may result in unwanted noise and vibration within the vehicle passenger compartment.
Conventional solutions to this vibration issue include controlling the engine operating conditions to minimize the magnitude and frequency range of the inertial torsional vibrations and tuning the powertrain mounts to minimize transmission of vibrations. However, the constraints placed on the engine/powertrain operation may impact the ability to achieve other desirable operating characteristics relative to responsiveness, fuel economy, and/or emissions, for example. Some known solutions control one or more counter-rotating elements to reduce or eliminate inertial torque reaction, such as disclosed in U.S. Pat. Nos. 5,551,928, and 5,570,615, for example. While these approaches may reduce the torque reaction on the powertrain structure, the increased mass also increases weight and reduces responsiveness of the system and may have an associated adverse impact on fuel economy.
Other solutions use an Integrated Starter Generator (ISG) as the counter rotating inertia as disclosed in U.S. Pat. No. 5,606,946; WO 03004845; and U.S. Pat. No. 6,516,770, for example. However, the present inventors have recognized that the benefits of counter rotating inertia as well as the fuel economy and performance benefits of an ISG diminish at higher engine rotational speeds.